Omega Five

Just beat the second stage of the game with any character in arcade mode. Learn the pattern of the snake mini-boss. The most dangerous part of this fight is getting hit by the body itself because it moves fairly quickly. Avoid using lock-ons for the mini-boss, as the turrets that circle will distract the fire. Shoot when the mini-boss drops its shields to attack, stay to the sides to avoid the quills, and avoid the turrets when they turn blue and chase you.